1. Field of the Invention
The present invention generally relates to recycling processes and apparatus, and more particularly to such an apparatus and process for recycling a polyolefin material end product.
2. Description of the Relevant Art
In recent years, the level of consciousness regarding environmental concerns has been greatly elevated One of today's major concerns relates to the disposal of various plastic products. It is not desirable to incinerate these materials, since it is virtually impossible to do so without releasing at least some toxic chemicals into the atmosphere. Besides posing a health problem, it has been discovered that toxic constituents in the atmosphere have been leading to the so-called "green house effect" or global warming.
Depositing waste products made from plastic materials into land fills is similarly an undesirable means of waste disposal, since it has been found that the majority of plastic consumer products will not decompose in the earth for hundreds of years. Even many of the biodegradable trash bags now being produced will not alleviate the landfill problem since the bags need to be exposed to air and water in order to decompose. As such, the present state of biodegradable products is not entirely satisfactory.
For these reasons, it would be desirable to have a process and apparatus which could recycle used plastic consumer goods into a product substantially comparable to the virgin polymeric raw material. This raw material could then be directly re-extruded or processed into new consumer goods. This could eventually lead to some type of equilibrium whereby there would be very little or no plastic waste which would need to be disposed of.
One known apparatus, such as that described in U.S. Pat. No. 3,815,833 uses a jet and anvil type mill. The thermoplastic material to be ground is injected into impact against a rotating anvil while also injecting a liquid. After some processing, the partially ground material formed is reinjected against the anvil by a gaseous fluid injector, with liquid continuing to be injected. The drawback of such an apparatus and process are several. Such an apparatus cannot directly grind used thermoplastic consumer end products--it is only suited for grinding already granular thermoplastic material. Further, such a process is very time consuming in that each run in the grinding chamber only partially grinds the thermoplastic material, thereby necessitating several reinjections into the chamber before a suitably ground granular thermoplastic material is obtained. And still further, such an apparatus is quite complex and expensive to build and maintain since the feed means, the gaseous fluid injector means and liquid injection means are rather intricate and subject to breakdown.
Therefore, it would be desirable to provide a process and apparatus for recycling a polyolefin material consumer end product which is inexpensive to build, simple to operate and cost effective to use. It would further be desirable to provide such a process and apparatus which can directly recycle plastic consumer products without any prior processing and which would give suitably ground plastic material in a relatively short period of time. Still further, it would be desirable to provide a process and apparatus which would give suitably ground plastic material directly ready for re-extrusion after one run in the apparatus.